Science Experiment: Why is the Sky Blue

In this experiment, I was supposed to learn about why the sky looks blue.  Light is made up of all the colours (except black, which is just no light), and sometimes when light is shining on something, only some of the colours get through to the other side.

To test this, we put some milk (just a little) in a jar full of water.  Then we shined a flashlight into the jar in a dark room.  When the light shone down on the top of the jar, the milky water on the top looked blue, like the sky.  When we shined the light through the side of the jar, the light coming out the other side looked red.

Here's the flashlight, jar and milky water we used:

The different colours are supposed to be because the particles of milk block the light so that short-wave light gets caught and bounced around (at the top of the sky), while long-wave light makes it through the other side (sky at sunset or sunrise).  I'm not sure it makes sense, because milk, the air in the atmosphere, and light aren't things that I think of as interacting.  My dad says the blue colour is actually just mostly light reflected from ozone molecules in the atmosphere -- that they are blue, just like my blue school bag.

My dad gave me a different example of only certain light passing through, and I thought this was much better:

Blood and flesh only lets through red light, like a sunset!